Lead-Free Nanoscale Metal/Oxidizer Composite for Electric Primers

ABSTRACT

A lead-free electric primer composition including a mixture of at least one metal having nanometer-sized particles with at least one oxidizer having nanometer-sized particles producing a metal(s)-oxidizer(s) nanocomposite, wherein the oxidizer(s) is present in an effective amount to substantially oxidize the metal(s), at least one gas generating material mixed with the metal(s)-oxidizer(s) nanocomposite producing a metal(s)-oxidizer(s)-gas generator(s) composition, at least one binder, the metal(s)-oxidizer(s)-gas generating composition is coated with the binder, and at least one conductive material.

The invention described herein may be manufactured and used by or forthe government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION

The present invention relates to lead-free percussion and electricprimer compositions, and more particularly, nanoscale primer compositionexhibiting reduced ignition delay in applications requiring high firingrates.

BACKGROUND OF THE INVENTION

Conventional primers for small and medium caliber ammunitionhistorically have been based on lead azide, lead styphnate, mercuryfulminate, and barium nitrate. These primer compositions also requireexpensive handling procedures during both production and disposal.Several tons of these toxic materials and heavy metals are used annuallyby U.S. commercial suppliers in the production of percussion primercompositions. The detrimental health effects of lead exposure in humanshave been extensively documented. The effects include gastrointestinal,cardiovascular, renal, immunological and hematological disorders, anddeath.

Environmental concerns about the hazards of lead exposure in themanufacturing process and during firing of small caliber ammunition inclosed firing ranges have prompted ammunition manufacturers to developlead-free primer composition alternatives primarily based ondiazodinitrophenol (DINOL) (3). While the DINOL based lead-free primersare sold for commercial applications, they do not meet more stringentmilitary requirements. Primer compositions used in military applicationsmust function reliably between −65° F. to 165° F. The functionalreliability of DINOL based primers degrade with decreasing temperature.The fact that externally mounted aircraft weapons are routinelysubjected to severe cold conditions, makes the low temperaturerequirement extremely important. Weapon misfire can have direconsequences. While DINOL primer compositions meet the requirements forcommercial applications, it currently does not meet militaryrequirements. In military applications the primer compositions areutilized primarily in primer cup assemblies.

U.S. Pat. No. 5,266,132 issued on Nov. 30, 1993 to Danen, et al., whichis assigned to the U.S. Government, teaches energetic nanoscalecompositions, which consist of layers of two reactive substances whichare aluminum and cupric oxide, wherein the layers are formed by thinfill deposition. In this composition each layer of aluminum is separatedfrom at least one layer of cupric oxide by a buffer layer. The all-upround action times for the nanoscale metal-metal oxide formulations aremuch too long (50-500 milliseconds), military requirements for DODapplication is less than 4 milliseconds.

U.S. Pat. No. 5,717,159 issued on Feb. 10, 1998 to Dixon, et al., alsoassigned to the U.S. Government, teaches the use of nanoscale compositesfor percussion primer application. The U.S. Department of the Armydeveloped and tested these MIC primers but found that the ignition delaywas greater than 50 milliseconds in comparison to less than 4milliseconds for conventional lead-based primers. These MIC primerignition delay times were not suitable for many military applicationsrequiring high firing rates.

There exists a need in the art for lead-free based nanoscale primercompositions having reduced ignition delays in applications requiringhigh firing rates.

SUMMARY OF THE INVENTION

The present invention relates to a lead-free percussion primercomposition comprising a mixture of at least one metal havingnanometer-sized particles with at least one oxidizer havingnanometer-sized particles producing a metal(s)-oxidizer(s)nanocomposite, wherein the oxidizer(s) is present in an effective amountto substantially oxidize the metal(s), at least one gas generatingmaterial (gas generator) mixed with the metal(s)-oxidizer(s)nanocomposite producing a metal(s)-oxidizer(s)-gas generator(s)composition, wherein the gas generating material comprisesBis-aminotetrazolyl-tetrazine (BTATz), and at least one binder, whereinthe metal(s)-oxidizer(s)-gas generating composition is coated with saidbinder.

In another embodiment, the lead-free electric primer compositioncomprises a mixture of at least one metal having nanometer-sizedparticles with at least one oxidizer having nanometer-sized particlesproducing a metal(s)-oxidizer(s) nanocomposite, wherein the oxidizer(s)is present in an effective amount to substantially oxidize the metal(s),at least one gas generating material (gas generator) mixed with themetal(s)-oxidizer(s) nanocomposite producing a metal(s)-oxidizer(s)-gasgenerator(s) composition, wherein the gas generating material comprisesBis-aminotetrazolyl-tetrazine (BTATz), at least one binder, saidmetal(s)-oxidizer(s)-gas generating composition is coated with thebinder, and at least one conductive material. The conductive materialmust be added after the binder coating for electric primers.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not to be viewed as being restrictive of the present invention, asclaimed. Further advantages of this invention will be apparent after areview of the following detailed description of the disclosedembodiments which are illustrated schematically in the accompanyingdrawings and in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a cartridge case showing theposition of the primer composition according to the present invention.

FIG. 1A is an exploded view of the electric primer cup assembly of thecartridge case shown in FIG. 1, wherein the exploded view illustratesthe position of the primer composition according to the presentinvention.

FIG. 2 is an alternative perspective view showing a cross section of theelectric primer cup assembly shown in FIG. 1, illustrating the positionof the primer cup assembly according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a lead-free percussion primercomposition comprising a mixture of at least one metal havingnanometer-sized particles with at least one oxidizer havingnanometer-sized particles producing a metal(s)-oxidizer(s)nanocomposite, wherein the oxidizer(s) is present in an effective amountto substantially oxidize the metal(s), at least one gas generatingmaterial (gas generator) mixed with the metal(s)-oxidizer(s)nanocomposite producing a metal(s)-oxidizer(s)-gas generator(s)composition, wherein the gas generating material comprisesbis-aminotetrazolyl-tetrazine (BTATz), and at least one binder, whereinthe metal(s)-oxidizer(s)-gas generating composition is coated with thebinder. In another embodiment of the lead-free percussion primercomposition, the composition further comprises at least one conductivematerial.

In another embodiment, the lead-free electric primer composition 300comprises, a mixture of at least one metal having nanometer-sizedparticles with at least one oxidizer having nanometer-sized particlesproducing a metal(s)-oxidizer(s) nanocomposite, wherein the oxidizer(s)is present in an effective amount to substantially oxidize the metal(s),at least one gas generating material (gas generator) mixed with themetal(s)-oxidizer(s) nanocomposite producing a metal(s)-oxidizer(s)-gasgenerator(s) composition, wherein the gas generating material comprisesbis-aminotetrazolyl-tetrazine (BTATz), at least one binder, themetal(s)-oxidizer(s)-gas generating composition is coated with thebinder, and at least one conductive material. The conductive materialmust be added after the binder coating for electric primers. In anotherembodiment, the conductive material(s) are uniformly coating themetal(s)-oxidizer(s)-gas generating composition.

The following description includes both lead-free percussion andelectric primer compositions of the present invention. The metal(s) inembodiments of the present invention are in the form of a powder, whichincludes at least one of aluminum, boron, titanium, zirconium,magnesium, hafnium, and any combination thereof. The metals includeparticle sizes of up to about 100 nanometers. In other embodiments, themetal(s) in the form of a powder the particle size are in the range ofabout 20 nm to about 80 nm or about 20 nm to about 60 nm.

The oxidizer(s) includes metal oxidizer(s) includes at least one ofMolybdenum Trioxides (MoO₃), Copper Oxides (CuO), Tungsten Oxides (WO₃),MoO₂, Molybdenum Oxides (MoO₂), and any combination thereof. When theoxidizer(s) are metal molybdate(s), the oxidizer(s) include M-MoO₄(M═Ag₂, Sr, Ca, (NH₄)₂. When the oxidizer(s) are metal nitrate(s), theoxidizer(s) include M—(NO₃)_(x) (M═Li, Na, K, Sr, Ca). When theoxidizer(s) are metal perchlorate(s), the oxidizers include M—(ClO₄)_(x)(M═Li, Na, K, Ca, Sr). In other embodiments, the oxidizer(s) are in theform of a powder including molybdenum trioxide. The oxidizer(s) are inthe form of a powder having a particle size of up to about 100nanometers. Other particles sizes of oxidizer(s) in the form of a powderinclude about 20 nm to about 80 nm or about 20 nm to about 60 nm.

The gas generating material(s) includes at least one ofBis-aminotetrazolyl-tetrazine (BTATz) salts. In other embodiments, thegas generating material(s) includes at least one of GuanidiniumBitetrazole (GBt), Bisguanidinium Azotetrazole (GAZT), Bis-tetrazole(BT), Triamino-guanidinum Nitrate (TAGN), 5-Aminotetrazole (5-AT), andany combination thereof In other embodiments, the gas generatingmaterials is nanosized but it is not necessary. In embodiments, the gasgenerating materials including BTATZ formulations prepared utilizedmicron sized particles. The primer composition includes about 5 weight %to about 50 weight % of the gas generating material(s). In otherembodiments, the primer compositions include about 20 to about 30 weight% of the gas generating material(s). The gas generating material(s)includes BTATZ being about 25 to about 35 wt % of the primercomposition. The gas generating material(s) being high nitrogencompounds with rapid decomposition rates. In embodiments of the presentinvention, gas generating materials would have a peak pressurizationtime of less than 100 microseconds and a pressurization rate of at least200,000 psi/s. The problem is that the pressurization rate is systemdependent. Sample size, apparatus volume and sample configuration (loosepowder, pellet, pellet densification, . . . ) affect the rate andoverall pressures observed.

The binder(s) includes at least one of Kel-F®, Teflon®, PolyethyleneOxide (PEO), Polyethylene Glycol (PEG), Gylcidyl Azide Polymer (GAP),Hydroxyl-Terminated Polybutadiene (HTPB), and any combination thereof.The fluoropolymer chemical “polychlorotrifluoroethylene” (PCTFE) is soldunder the trademark “Kel-F.” The registrant is M. W. Kellogg Company, aDelaware Corporation, 225 Broadway Jersey City, N.J.. The flouropolymerresins, films, and fibers “polytetrafluoroethylene (PTFE),perfluoroalkoxy (PFA), and fluorinated ethylene polymer (FEP) is soldunder the trademark “Teflon.” The registrant is E. L Du Pont De Nemours,a Delaware Corporation, 1007 Market St. Wilmington, Del. In otherembodiments, the binder(s) includes at least one of Kel-F® and Teflon®.The binder(s) in other embodiments include a range of about 2 to about25 weight % of or about 4 weight % of the primer composition. Thebinder(s) include a particle size of up to about 100 nanometers. Thebinder(s) is coated onto the metal/oxidizer/gas generating compositionin varying thicknesses or uniformly.

In other embodiments further comprise conductive additive(s) having aparticle size of up to about 100 nanometers. Some of the conductiveadditive(s) includes at least one of carbon black, conductive polymers,conductive submicron metals including (gold, platinum, palladium, andnickel), calcium silicide, and any combination thereof.

In the lead-free electric primer composition embodiments, at least oneconductive material is included. Conductive material is added after thebinder coating. The conductive material(s) includes at least one ofhaving a particle size of up to about 100 nanometers.

The electric and percussion primers of the present invention are unlikeconventional primers that contain primary explosives. The nanoscalemetal fuel and oxidizer are ignited either by impact (percussion primer)or by electrical ohmic heating (electric primer). The rapid exothermicreaction between the metal fuel and oxidizer initiates rapiddecomposition of the gas generator compound that pushes the hotcombustion products into the propellant, igniting the propellant bed.The gas generating material is extremely important for reducing ignitiondelay times from 50 to less than 4 milliseconds.

In embodiments of the percussion and electric primer compositions, theBis-aminotetrazolyl-tetrazine (BTATZ) and Kel-F® are mixed with thenanoscale aluminum and molybdenum trioxide. In embodiments of thepercussion primer compositions, the composition comprises of about 31weight % metal (aluminum), about 37 weight % oxidizer (molybdenumtrioxide), about 30 weight % gas generating material (BTATZ), and about2 weight % binder (Kel-F®). In other embodiments of the electric primercompositions, the composition comprises of about 30 weight % metal(aluminum), about 36 weight % oxidizer (molybdenum trioxide), about 30weight % gas generating material (BTATZ), about 2 weight % binder(Kel-F®), and about 2 weight % additive (carbon black). It was foundthat about 2 weight % of binder showed improved pressed pellet integrityand improved ignition reliability. In addition, about 2 weight % ofcarbon showed reliable electric ignition and about 30 weight % of BTATZshowed reduced all-up round action times.

Carbon black is added for the electric primer application. Where theprimer composition according to the present invention is comprised of ananoscale metal powder, a nanoscale metal oxidizer, a gas generatormaterial, a binder for percussion primer, and conductive material isadded for electric primer.

Experimental Results

The following preparation was performed in processing the primercompositions of the present invention. Others have found thatheat-treated MoO₃ and ultrasonic mixing of the primer composition causesminimal aging. A nanoscale Al/MoO₃ composite composed of 45 weight % Al(52.8 nm, 73.8% Active Al) and 55 weight % MoO₃ was purchased fromTechnanogy, NSWCIH. The MoO₃ in the Al/MoO₃ composite was acquired fromClimax® and was lightly ground using a mortar and pestle and sievedthrough a 270 mesh sieve. Bis-aminotetrazolyl-tetrazine (BTATZ) preparedand purified at China Lake was lightly ground with a mortar and pestleand sieved through a 270-mesh sieve. Kel-F® also known aspolychlorotrifluoroethylene (PCTFE) is a fluorochemical product and wasused and received from the Kellogg® Company. Carbon was obtained fromChevron-Phillip® and sieved through a 270 mesh sieved prior to use.

Nanoscale material performance degrades with time. AlO passivationthickness dramatically affects aging in, air. Al with 1.7 nm oxide layerexhibits a dramatic loss in active Al over time and Al with 2.7 nm oxidelayer loses some active Al initially but stabilizes after 2 weeks. SomeMoO₃ changes color, loses surface area, absorbs water and undergoes aphase change over time. The MoO₃ hydrate catalyzes the hydrolysis ofnanoscale aluminum powders. It was found that heat treatment to the aphase reduces aging effects. This data showed that mixing conditionsaffect material performance and aging. The mixing techniques utilizedfor Al/MoO₃ composites in the present invention showed no aging after >6months.

In the first example, 0.712 g of the Al/MoO₃ composite and 0.320 g ofBTATZ were transferred into a vial and mixed with a shaker for about 2minutes. Approximately 0.012 g of Kel-F® was added and dissolved in 10ml of CH₂Cl₂ to the mixture. The solvent (CH₂Cl₂) was evaporated off theslurry mixture by blowing nitrogen gas over its surface for about 2hours. The product was dried under vacuum for about 2 hours. Carbon(0.021 g) was added to the Al/MoO₃/Kel-F® solid and mixed with a shaker(Electric Primer).

In the second example, 0.846 g of the Al/MoO₃ composite and 0.220 g ofBTATZ was transferred into a vial and mixed with a shaker for about 2minutes. Approximately 0.027 g of Kel-F® was added and dissolved in 10ml of CH₂Cl₂ to the mixture. The solvent was evaporated off the slurrymixture by blowing nitrogen gas over its surface for about 2 hours. Theproduct was dried under vacuum for 2 hours. Carbon (0.024 g) was addedto the Al/MoO₃/Kel-F® solid and mixed with a shaker (Electric Primer).

In the third example, 1.038 g of the Al/MoO₃ composite and 0.125 g ofBTATZ was transferred into a vial and mixed with a shaker for about 2minutes. Approximately, 0.026 g of Kel-F® was added and dissolved in 11ml of CH₂Cl₂ to the mixture. The solvent was evaporated off the slurrymixture by blowing nitrogen gas over its surface for about 2 hours. Theproduct was dried under vacuum for 12 hours. Carbon (0.021 g) was addedto the Al/MoO₃/Kel-F® solid and mixed with a shaker (Electric Primer).

In the fourth example, 0.733 g of the Al/MoO₃ composite and 0.314 g weremixed in a vial using a shaker for about 2 minutes. Approximately 0.021g of Kel-F® was added and dissolved in 5 ml of CH₂Cl₂ to the mixture.The solvent was evaporated off the slurry mixture by blowing nitrogengas over its surface for about 2 hours. The product was dried undervacuum for 12 hours (Percussion Primer).

In the fifth example, 0.082 g of Kel-F® was dissolved in 35 ml ofCH₂Cl₂. Approximately, 2.644 g of the Al/MoO₃ composite was added to theKel-F®/CH₂Cl₂ solution and stirred for 1 minute using a magnetic stirbarand magnetic stirrer. Approximately 1.202 g of BTATZ was added to themixtures and mixing continued for 2 minutes. The solvent was evaporatedoff the slurry mixture by blowing nitrogen gas over its surface forabout 2 hours. The product was dried under vacuum for about 12 hours.Approximately 0.081 g of carbon was added to the dried solid and mixedwith a shaker for 2 minutes (Electric Primer).

In the sixth example, 0.020 g of Polyethylene Glycol (PEG) was added anddissolved in 25 ml of hexane. Approximately 12.5 ml of the PEG solutionwas added to the 0.712 g of the Al/MoO₃ composite and 12.5 ml to 0.305 gof BTATZ in 2 separate vials. The 2 mixtures were combined and mixed for2 minutes using a magnetic stir-bar and magnetic stirrer. The solventwas evaporated off the slurry mixture by blowing nitrogen gas over itssurface for about 2 hours. The product was dried under vacuum for 12hours. (Percussion Primer).

FIGS. 1, 1A and 2 illustrate cross sectional views of an electric primercup assembly showing the placement of the primer compositions of thepresent invention. One embodiment of an electric primer cup assembly 100includes an insulator 120/210, button 110, cup 130/220, paper 140/240,support cup 250, cartridge case 230 and energetic material 300/400. Inan embodiment of the present invention, the brass button 110 and thebrass primer cup 130 serve as electrodes with an insulator layer 120between them. Energetic material 300 is consolidated into the primer cupusing a paper separator 140 and a press. The paper is used to preventenergetic material sticking to the rod used consolidate the energeticmaterial. A support cup is inserted to hold the energetic material andpaper in the desired configuration. The primer cup assembly 100 is theninserted into the loaded cartridge case 230. To initiate firing of around, a potential is applied through the electrodes (button and cup)that rapidly heat the energetic material via ohmic heating. The rapidrise in temperature ignites the primer energetic material. The hotreaction products are transported into and ignite the propellant bed.The hot gases formed from the propellant propel the projectile out ofthe casing.

Major advantages of the present invention include, but are not limitedto, use in lead-free percussion and electric primers, meets militaryrequired action time of 4 ms, and has application for small, medium, andlarge caliber ammunition, flash bang grenades (stun-grenades),indoor/outdoor pyrotechnics, flares, mini-thrusters for missileguidance, anti-tamper devices, and additives for explosives andpropellants.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

1. A lead-free electric primer composition comprising: a mixture of atleast one metal having nanometer-sized particles with at least oneoxidizer having nanometer-sized particles producing ametal(s)-oxidizer(s) nanocomposite, wherein said oxidizer(s) is presentin an effective amount to substantially oxidize said metal(s); at leastone gas generating material (gas generator) mixed with saidmetal(s)-oxidizer(s) nanocomposite producing a metal(s)-oxidizer(s)-gasgenerator(s) composition, wherein said gas generating material comprisesbis-aminotetrazolyltetrazine (BTATz); at least one binder, saidmetal(s)-oxidizer(s)-gas generating material composition is coated withsaid binder; and at least one conductive material.
 2. The compositionaccording to claim 1, wherein said metal(s) being in the form of apowder which comprises at least one of aluminum, boron, titanium,zirconium, magnesium, hafnium, and any combination thereof.
 3. Thecomposition according to claim 1, wherein said metal is a powder havinga particle size of up to about 100 nanometers.
 4. The compositionaccording to claim 1, wherein said metal is a powder having a particlesize of about 20 nm to about 80 nm.
 5. The composition according toclaim 4, wherein said metal is a powder having a particle size of about20 nm to about 60 nm.
 6. The composition according to claim 1, whereinsaid oxidizer(s) includes metal oxidizer(s) comprising at least one ofMolybdenum Trioxide (MoO₃), Copper Oxide (CuO), Tungsten Oxide (WO₃),Molybdenum Dioxide (MoO₂), and any combination thereof. 7-9. (canceled)10. The composition according to claim 1, wherein said oxidizer(s) beingin the form of a powder is molybdenum trioxide.
 11. The compositionaccording to claim 1, wherein said oxidizer is a powder having aparticle size of up to about 100 nanometers.
 12. The compositionaccording to claim 1, wherein said oxidizer is a powder having aparticle size of about 20 nm to about 80 nm.
 13. The compositionaccording to claim 12, wherein said oxidizer is a powder having aparticle size of about 20 nm to about 60 nm.
 14. The compositionaccording to claim 1, wherein said gas generating material(s) comprisesat least one of bis-aminotetrazolyl-tetrazine (BTATz) salts. 15.(canceled)
 16. The composition according to claim 1, wherein said gasgenerating material comprises about 5 to about 50 weight % of saidprimer composition.
 17. The composition according to claim 16, whereinsaid gas generating material comprises about 25 to about 35 weight % ofsaid primer composition.
 18. The composition according to claim 1,wherein said gas generating material comprises about 20 to about 30weight % of said primer composition.
 19. The composition according toclaim 1, wherein said binder(s) comprises at least one ofpolychlorotrifluoroethylene (PCTFE), Polyethylene Oxide (PEO),Polyethylene Glycol (PEG), Gylcidyl Azide Polymer (GAP),Hydroxyl-Terminated Polybutadiene (HTPB), and any combination thereof.20. The composition according to claim 1, wherein said binder comprisesat least one of polychlorotrifluoroethylene (PCTFE).
 21. The compositionaccording to claim 1, wherein said primer composition includes about 2to about 25 weight % of said binder.
 22. The composition according toclaim 21, wherein said primer composition includes about 4 weight % ofsaid binder.
 23. The composition according to claim 1, wherein saidbinder is a powder having a particle size of up to about 100 nanometers.24. The composition according to claim 1, wherein said conductivematerial is a powder having a particle size of up to about 100nanometers.
 25. The composition according to claim 1, further comprisingconductive additive having a particle size of up to about 100nanometers.
 26. The composition according to claim 1, wherein saidconductive material comprises at least one of carbon black.
 27. Thecomposition of claim 1, wherein said at least one metal is a powder,having nanometer-sized particles, including Aluminum.
 28. A lead-freeelectric primer composition comprising: a metal powder, havingnanometer-sized particles, including Aluminum; an oxidizer powder,having nanometer-sized particles, including molybdenum trioxide (MoO₃)in sufficient amount to substantially oxidize said Aluminum; a gasgenerating material including bis-aminotetrazolyl-tetrazine (BTATz); abinder including polychlorotrifluoroethylene (PCTFE); and a conductivematerial including carbon black in sufficient amount to render thecomposition electrically conducting.